KR20070000869A - Optical transmission system for integrated wired/wireless service - Google Patents

Abstract

An optical transmission system for a wired/wireless integrated service is provided to enable a Mach-Zehnder electric filter to receive a signal converted into an electric analog signal in a light receiving element, dichotomize the received signal, transfer phases of each dichotomized signal, and synthesize the signal, thereby reducing the influence of adjacent channels on a digital signal and an analog signal simultaneously received, and reducing intermodulation distortion generated when plural analog signals are simultaneously inputted into the optical transmission system. An optical transmission system for a wired/wireless integrated service comprises the followings: the first signal synthesizer(313); an LED(Light Emitting Diode)(315); an optical coupler(317); a light receiving element(319); a Mach-Zehnder electric filter(A) which receives a signal converted into an electric analog signal in the light receiving element(319), dichotomizes the received signal, transfers phases of each dichotomized signal, and synthesizes the signal; the first filter(B) for removing noise before performing phase transfer of the first signal dichotomized in the Mach-Zehnder electric filter(A), and then synthesizing the noise-removed signal with the first signal of the dichotomized digital signals; and the second filter(C) for removing noise before performing phase transfer of the second signal dichotomized in the Mach-Zehnder electric filter(A), and then synthesizing the noise-removed signal with the second signal of the dichotomized digital signals.

Description

Optical Transmission System for Wired / Wireless Integrated Service {Optical Transmission System for Integrated Wired / Wireless Service}

1 is a view for schematically explaining a general wired and wireless integrated network,

2 is a view showing the configuration of a general optical transmission system;

3 is a view for explaining a conventional wired and wireless signal transmission method,

4 is a view for explaining a conventional analog signal transmission method,

5 is a view showing the configuration of a light transmission system using a general Mahzander electric filter,

6 is a diagram showing an RF frequency spectrum of a signal transmitted in the optical transmission system of FIG.

7 is a view showing the configuration of an optical transmission system using a feedback harmonic injection technique according to the present invention,

FIG. 8 is a diagram illustrating a transmission side-side photodiode of the optical transmission system of FIG. A diagram showing the spectrum of the signal being measured,

9 is a view showing a frequency spectrum suppressed by the optical transmission system of FIG. 7,

10 is a view showing the configuration of an optical transmission system using the Mahzander electric filter and feedback harmonic injection technique according to the present invention.

<Description of the symbols for the main parts of the drawings>

10, 105, 109, 201, 303, 307, 309, 313: signal synthesis section

12, 31, 33, 111, 203, 315: laser diode

14, 113, 207, 213, 319: photodiode 20: external modulator

16, 101, 301, 321: signal distribution unit

103, 107, 211, 305, 311: phase shifter 117: low pass filter

119, 209, 323, 325: band pass filter 205, 317: optical coupler

The present invention relates to an optical transmission system for wired / wireless integrated service, and more particularly to an optical transmission system for wired / wireless integrated service for reducing the influence of an adjacent channel generated when simultaneously transmitting and receiving digital signals and analog signals.

The communication service to date has been divided into wired and wireless, and service was provided considering the characteristics of each area. However, as the number of multimedia services provided on the wired / wireless Internet increases, users who use them want to receive services regardless of time and place. Accordingly, the necessity of a wired / wireless integrated network has emerged, and a wired / wireless integrated service has emerged that combines wired broadband and mobility of a wireless network.

1 is a diagram schematically illustrating a general wired / wireless integrated network.

Wired / wireless integrated networks are used to connect digital and wireless signals to wired / wireless networks, including mobile communication networks, wireless LANs, the Internet, and public switched telephone networks. As an integrated network capable of transmitting and receiving analog signals to be used as an optical network, an optical transmission system is located in a wired / wireless integrated network and modulates analog or digital signals received from different communication networks into optical signals to provide wired and wireless networking services. Transfer it to the optical exchange built in.

2 is a diagram illustrating a configuration of a general optical transmission system.

The signal synthesizing unit 10 of FIG. 2 (a) synthesizes the digital signal used as the wired signal and the analog signal used as the wireless signal, and then synthesizes it, and then the laser diode 12 as a light emitting element to perform optical communication. To pass.

The laser diode 12 modulates an electric signal transmitted from the signal synthesizing unit 10 into an optical signal and transmits the optical signal to the optical fiber cable.

When the photodiode 14 as a light receiving element receives an optical signal that is optically modulated by the laser diode 12 and transmitted through an optical fiber cable, the photodiode 14 is converted into an original analog signal and a digital signal, and then the signal distribution unit 16. The analog signal is separated into an analog signal and a digital signal, and the separated analog signal is removed from the bandpass filter unit, amplified by an amplifier, and then transmitted to the mobile communication terminal. In addition, the separated digital signal is removed from the low pass filter unit and transmitted to the wired terminal.

Unlike the method of FIG. 2A, the method of FIG. 2B does not directly modulate and transmit a signal, but modulates the signal using an external modulator 20, and then transmits the signal to the photodiode 14 through an optical fiber. Here, the external modulator 20 is any one of an ultrasonic modulator, a modulator using an electro-optic or magneto-optic effect such as a curl effect or a Faraday effect, and a modulator using a change in optical properties in a PN junction or superlattice structure of a semiconductor. .

FIG. 2 (c) optically modulates the wireless signal and the wired signal in each of the laser diodes 31 and 33 by using wavelength division multiplexing, and transmits the optical signal to the photodiode 14 through an optical fiber cable.

The signal transmission method described in FIG. 2 is to transmit digital signals and analog signals in a distant frequency range such as 10 Gbps and 60 GHz, 2.5 Gbps and 5.5 GHz, respectively, if the frequency range of the wired / wireless signal to be transmitted is 622 Mbps and 900 MHz. Alternatively, when 1.2 Gbps and 1.8 GHz are in close proximity, as shown in FIG. 3, interference may occur due to influence of adjacent wired and wireless signals.

In addition, the digital / analog transmission system to date has transmitted only an analog signal when transmitting an analog signal. If the analog frequency signals f1 and f2 are simultaneously transmitted as shown in FIG. 4, a nonlinear element such as a laser diode is used. There is a problem that intermodulation distortion (IMD) inevitably occurs.

In particular, the generation of the tertiary IMD, which is a synthesized 2f1-f2 and 2f2-f1 component, is generally difficult to eliminate because the two signals to be transmitted are adjacent to both sides of f1 and f2. Since it cannot be used, there is a problem that adversely affects in terms of the frequency band used.

The present invention has been made to solve the above-described problems, it is possible to reduce the effect of the adjacent channel caused by the simultaneous input of the digital signal and the analog signal at the wired and wireless signal transmitter, a plurality of analog signals input to the wired and wireless signal transmitter There is a technical problem to provide an optical transmission system for wired / wireless integrated service using the Mahzander electric filter technology and feedback harmonic injection technology that can reduce intermodulation distortion.

The present invention for achieving the above object is an optical transmission system for wired / wireless integrated service connected to a wired / wireless communication network, receiving a digital signal to be used as a wired signal and an analog signal to be used as a wireless signal, synthesized, modulated and transmitted.

A first signal synthesizer for receiving an analog signal; A light emitting device which optically modulates and outputs an analog signal transmitted from the first signal synthesizing unit; An optical coupler for receiving an optical signal transmitted from the light emitting device, dividing the optical signal, and outputting the divided signal; A light receiving element which receives one of the signals divided by the optical coupler and converts the signal into an electrical signal; A Mahzander electrical filter unit which receives a signal converted into an electrical analog signal from the light receiving element, divides the synthesized signal, shifts the phase of each divided signal, and synthesizes the converted signal; A first filtering unit which removes noise before phase shifting the bisected first signal by the Mahzander electrical filter unit and synthesizes the first signal from the bisected digital signal; The first signal synthesizing unit includes a second filtering unit which removes noise before phase shifting the second divided signal by the Mahzander electrical filter unit and synthesizes it with a second signal of the divided digital signals. A signal output from the filter unit and an analog are synthesized and output, and the output signal is light modulated and transmitted.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 5 is a diagram illustrating a configuration of an optical transmission system using a general Mahzander electric filter, and will be described with reference to FIG. 6, which shows an RF frequency spectrum of a signal transmitted in the optical transmission system of FIG. 5.

The optical transmission system using the Mahzander electric filter is connected in series with the first signal distribution unit 101 and the first signal distribution unit 101 which receive a digital signal to be used as a wired signal from the first signal distribution unit 101. The first phase shifter 103, which phase shifts a specific frequency of the output digital signal, is connected in series with the first phase shifter 103 to receive a digital signal that is phase shifted by the first phase shifter 103. The first signal combiner 105 is included.

In addition, the optical transmission system is connected in series between the first signal distribution unit 101 and the first signal synthesizing unit 105 and arranged in parallel with the first phase shifter 103, the first signal distribution unit 101. ) Is connected in series with the second phase shifter 107 and the first signal synthesizer 105 which phase shifts the digital signal outputted from the digital signal, and receives the digital signal output from the first signal synthesizer 105, and wirelessly And a second signal synthesizing unit 109 for receiving and synthesizing an analog signal to be used as a signal and transmitting the synthesized signal to the laser diode 111 as a light emitting device.

In addition, the optical transmission system is connected in series with the second signal synthesizing unit 109 to optically modulate an electrical signal output from the second signal synthesizing unit 109 to the photodiode 113 as a light receiving element through an optical fiber cable. The photodiode 113 and the photodiode 113 which transmit the optical signal output from the laser diode 111 through the optical fiber, the laser diode 111 to transmit, and then transmit the optical signal to the second signal distribution unit 115. And a second signal distribution unit 115 which separates the signal outputted from the signal and transmits it to any one of the low pass filter 117 and the band pass filter 119 according to its characteristics.

The digital signal separated by the second signal distributor 115 is removed from the low pass filter 117 and is transmitted to the wired terminal. The separated analog signal has noise from the band pass filter 119. It is removed, amplified by an amplifier and transmitted to the mobile communication terminal.

In the optical transmission system using the Mahzander electric filter of the portion indicated by the dotted line in FIG. 5 is configured to minimize the influence of the adjacent channel when transmitting the digital signal and the analog signal at the same time, the Mahzander electric filter is a frequency of a specific band The component can be suppressed. For example, when the optical transmission system disclosed in FIG. 5 transmits a 1.2 Gbps digital signal and an 1.8 GHz analog signal, it may be confirmed that noise of 20 dB or more is reduced as shown in FIG. 6. Here, the first phase shifter 103 and the second phase shifter 107 of the optical transmission system are adjustable to suppress the wide band frequency components.

6 is a diagram showing the RF frequency spectrum when no filter is used for signal transmission (X mark), when a general filter is used (○ mark), and when a Mach-Zender electric filter is used (● mark). In the case of using a Mahzander electric filter, it can be seen that the interference signal component is suppressed with a remarkable difference compared to when using a general filter or no filter.

7 is a view showing the configuration of an optical transmission system using a feedback harmonic injection technique according to the present invention, in which the optical transmission system of FIGS. 8 and 7 shows a spectral diagram of a spectrum of a signal fed back through a photodiode. The following describes the frequency spectrum suppressed by FIG. 9.

The optical transmission system using feedback harmonic injection technology is connected in series with a first signal synthesizing unit 201 and a first signal synthesizing unit 201 for simultaneously receiving and synthesizing two analog signals f1 and f2 to be used as wireless signals. When receiving the laser diode 203 as a light emitting element for light modulating the analog signals f1 and f2 output from the first signal synthesizing unit 201 and the optical signal output from the laser diode 203, the magnitude of the signal is 5: After dividing by 5, one of the signals whose power is cut in half includes an optical coupler 205 which transmits to the photodiode 207 of the transmitting end and the other to the photodiode 213 of the receiving end.

In addition, an optical transmission system is connected to the optical coupler 205 and connected in series with a photodiode 207 and a photodiode 207 as light receiving elements for converting an optical signal transmitted from the optical coupler 205 into an electrical signal. And a band pass filter unit 209 and a band pass filter unit 209 and the first signal combination unit 201 for filtering a 2f2 signal among a plurality of harmonic signals output from the photodiode 207 are connected in series. The apparatus further includes a phase shifter 211 which transmits a specific frequency 2f2 of the signal output from the pass filter 209 to the first signal synthesis unit 201 after the phase shifts 2f2-f1.

Thereafter, the first signal synthesizing unit 201 synthesizes the 2f2-f1 signals and the analog signals f1 and f2 output from the phase shifter 211 and transmits them to the laser diode 203. Then, 2f2-f1, the third order intermodulation distortion signal of the two signals f1 and f2, is canceled by the feedback signal 2f2.

The spectrum of the signal output from the optical coupler 205 and converted into an electrical signal by the photodiode 207 is a form in which various frequency components coexist as shown in FIG. 8. Here, harmonic components 2f1 and 2f2 are generated, and the bandpass filter unit 209 filters the 2f2 signal.

In addition, the signal transmitted through the phase shifter 211 and the first signal synthesizing unit 201 after the feedback is excluded from the 1.1 GHz analog signal and the 1.2 GHz analog signal as shown in FIG. 9. It can be seen that the signal of 1.3 GHz, which is the third order intermodulation distortion component, is suppressed.

10 is a view showing the configuration of an optical transmission system using the Mahzander electrical filter and feedback harmonic injection technology according to the present invention, when the digital transmission signal and the analog signal is simultaneously received by the optical transmission system to reduce the effect of adjacent channels, Is a diagram illustrating an example of a configuration for reducing intermodulation distortion that occurs when an analog signal is received.

The optical transmission system includes a first signal synthesizing unit 313 for receiving an analog signal, a laser diode 315 as a light emitting element for optically modulating and outputting an analog signal transmitted from the first signal synthesizing unit 313, and a laser diode 315. A photodiode as a light receiving element for receiving and dividing an optical signal transmitted from the optical signal, and receiving any one of the optical signal from the optical coupler 317 and the optical coupler 317, respectively, and converting the optical signal into an electrical signal. 319, the makzen electric filter unit (A), the makzen electric filter unit for dividing and receiving the signal converted into an electrical analog signal from the photodiode 319 and shifting the phase of each divided signal (A), A first filtering unit (B) that removes noise before phase shifting the first divided signal in A) and synthesizes the first signal among the divided digital signals, and

And a second filtering unit C which removes noise before phase shifting the second signal divided by the Mahzander electrical filter unit A and synthesizes the second signal of the divided digital signals.

When the first signal synthesizing unit 313 synthesizes and outputs an analog signal and an output from the Mahzander electrical filter unit A, the output signal is output after being optically modulated by the laser diode 315.

In more detail, the Mahzander electrical filter unit A receives the analog signal converted from the photodiode 319 as a light receiving element into an electrical signal, splits and outputs the first signal distributor 321 and the first filtering unit. A first phase shifter 305 for shifting the phase of the first signal divided into two parts from (B) and a second phase shifter for shifting the phase of a second signal divided into two parts from the second filtering unit C; 311 and a second signal synthesizer 307 for synthesizing the signals output from the first phase shifter 305 and the second phase shifter 311 and outputting the synthesized signals to the first signal synthesizer 313. .

The first filtering unit B is output from the first bandpass filter unit 323 and the first bandpass filter unit 323 which remove noise of the first signal which is divided and output from the first signal distribution unit 321. And a third signal synthesizing unit 303 for synthesizing a first signal of the divided signal and the divided digital signal. Here, the digital signal is input to the second signal distribution unit 301 and divided into two.

The second filtering unit C outputs from the second bandpass filter unit 325 and the second bandpass filter unit 325 which remove noise of the second signal which is divided and output from the first signal distribution unit 321. And a fourth signal synthesizing unit 309 for synthesizing a second signal among the divided signals and the divided digital signals. Here, the digital signal is input to the second signal distribution unit 301 and divided into two.

For example, the process of FIG. 10 is developed as follows.

와 상호변조 성분(intermodulation products)인

(

= 0, 1, 2, 3, ...)를 포함한다.When the analog signals f1 and f2 are input to a laser diode which is a nonlinear device, the electrical signals received at the receiving end of the optical transmission system are harmonics in addition to the fundamental frequencies f1 and f2.

And intermodulation products

(

= 0, 1, 2, 3, ...).

The two signals f1 and f2 input to the optical transmission system are represented by electric fields as shown in Equation 1, respectively, and Equation 2 can be obtained by adding the two signals in the signal synthesis unit.

은 광 전송 시스템의 전달함수 크기를 의미하며, DC는 직류성분을 의미한다. The laser diode, which is a nonlinear device, loads an analog signal f1 and f2 on an optical signal, modulates the size, and then transmits the signal to a photodiode. From here,

Denotes the magnitude of the transfer function of the optical transmission system, and DC denotes the DC component.

It can be seen that there are many components by substituting the electric field values of f1 and f2 into Equation 3 and expanding them into trigonometric functions.

)와 피드백 고조파 성분인

와

을 합한다.The optical transmission system uses the analog signals f1 and f2 (to remove the third-order intermodulation signal generated when multiple analog signals are transmitted and received.

) And feedback harmonic components

Wow

Add up.

,

와

를 합한 수학식 5와 같다.Accordingly, the electrical signal received by the fourth signal synthesizing unit 313 of FIG. 10 and transmitted to the laser diode 315 is

,

Wow

Is equal to Equation 5.

The laser diode 315 optically modulates the electrical signal and then transmits the optical signal to the photodiode 319 through the optical coupler 317.

The electrical signal received by the photodiode 319 located at the transmission end of the optical transmission system is represented by Equation 3, and when only some of the terms derived from Equation 3 are extracted, Equation 6 is obtained.

을 소거하기 위해

을 추가로 입력한 결과가 된다.That is, the optical transmission system

To mute

Results in an additional input.

은

이 되므로 제거하고자 하는 성분과 추가된 성분의 크기와 위상이 같도록 조절하면 서로 상쇄시켜 제거할 수 있다.

silver

This can be removed by canceling each other by adjusting the size and phase of the component to be added and the component to be removed.

을 제거하기 위해

의 크기(

)와 위상(

)을 송신단에서 조절한다. That is, by adjusting the phase shifter,

To remove

Size (

) And phase (

In the transmitter.

As such, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without changing the technical spirit or essential features thereof. Therefore, the above-described embodiments are to be understood as illustrative in all respects and not as restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

As described above, the optical transmission system for the wired / wireless integrated service of the present invention has an advantage of reducing the influence of the adjacent channel on the digital signal and the analog signal simultaneously received by the optical transmission system of the wired / wireless integrated network.

In addition, the present invention has an advantage in that when a plurality of analog signals are simultaneously input to the optical transmission system, the resulting intermodulation distortion can be reduced.

In addition, the present invention has the advantage that it is possible to prevent the crosstalk of the signal when the wired and wireless signals simultaneously.

Claims (6)

As an optical transmission system for wired / wireless integrated service connected to a wired / wireless communication network, a digital signal to be used as a wired signal and an analog signal to be used as a wireless signal are received, synthesized, modulated, and transmitted. A first signal synthesizer for receiving an analog signal; A light emitting device which optically modulates and outputs an analog signal transmitted from the first signal synthesizing unit; An optical coupler for receiving an optical signal transmitted from the light emitting device, dividing the optical signal, and outputting the divided signal; A light receiving element which receives one of the signals divided by the optical coupler and converts the signal into an electrical signal; A Mahzander electrical filter unit which receives a signal converted into an electrical analog signal from the light receiving element, divides the synthesized signal, shifts the phase of each divided signal, and synthesizes the converted signal; A first filtering unit which removes noise before phase shifting the bisected first signal by the Mahzander electrical filter unit and synthesizes the first signal from the bisected digital signal; And A second filtering unit which removes noise before phase shifting the second divided signal by the Mahzander electrical filter unit and synthesizes the second signal among the divided digital signals; The optical signal transmission system of claim 1, wherein the first signal synthesizing unit synthesizes and outputs an analog signal and an output signal from the Mahzander electrical filter unit, and the output signal is optically modulated and transmitted. The method of claim 1, The Mahzander electrical filter unit, A signal distribution unit for receiving an analog signal converted from the light receiving element into an electrical signal and dividing the signal into two parts; A first phase shifter for shifting the phase of the first signal which is divided and output from the first filtering unit; A second phase shifter for shifting the phase of the second signal which is divided and output from the second filtering unit; And A second signal synthesizing unit for synthesizing signals output from the first phase shifter and the second phase shifter and outputting the synthesized signal to the first signal synthesizing unit; Optical transmission system comprising a. The method of claim 2, The first filtering unit, A bandpass filter to remove noise of the first signal which is divided and output from the signal distributor; And A third signal synthesizing unit for synthesizing a first signal of the signal output from the band pass filter unit and the divided digital signal; Optical transmission system comprising a. The method of claim 2, The second filtering unit, A bandpass filter for removing noise of the second signal which is divided and output from the signal distributor; And A fourth signal synthesizing unit for synthesizing a second signal of the signal output from the band pass filter unit and the divided digital signal; Optical transmission system comprising a. The method of claim 1, The light emitting device is a laser diode, characterized in that the laser diode. The method of claim 1, And the light receiving element is a photodiode.

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